Ah, I see the scene you're talking about. The implication I've seen from other scenes is that nobody understands what's going on in the freak attack the first time they see it, because it's so fast (and/or crazy). So the first time he sees it is just surprise, and then after that he realizes what's going on and thinks it's freaky.

(I just saw your edit. I don't think you need to be a 12-year-old boy to love that.)